Synthesis of nanostructured nickel-iron catalysts for sustainable methane production via CO₂ hydrogenation

NiFe2O4 catalysts supported on gamma Al2O3, stabilized ZrO2, and mixed gamma Al2O3-ZrO2 were synthesized using the deposition-precipitation method. The catalytic performance of the NiFe/gamma Al2O3, NiFe/YSZ and NiFe/gamma Al2O3-YSZ catalysts for CO2 hydrogenation to methane was compared with the unsupported NiFe2O4 catalyst. The role of the catalyst preparation, the type and use of support, and the spinel structure in the ultimate catalytic performance were illustrated by surface characterization techniques and CO2 methanation tests. Nickel ferrite formation was confirmed by FT-IR (similar to 600 cm(-)(1) band) and XRD patterns matching the cubic spinel structure. The homogeneously distributed nickel ferrite nanoparticles over the gamma Al2O3 surface were evidenced by its broadened XRD peaks and assigned to the facilitated intrapore diffusion from the pore mouths of gamma Al2O3 in 13.4 nm. All FE-SEM images showed < 10 nm nanocrystals for supported catalysts. NiFe/ gamma Al2O3, with the largest specific surface area, was seen to be favorable, possessing the highest total basic site concentration. TPR profile of NiFe2O4 on gamma Al2O3 exhibited lower peak intensities with broadening and this was argued as a more uniform distribution of nickel ferrite nanoparticles inside the cavities of gamma Al2O3. The highest CO2 and H-2 conversions of around 79-83 % have been recorded for gamma Al2O3 and mixed gamma Al2O3-ZrO2 catalysts without any CO formation. All these have pointed out the fact that nickel ferrite interaction has been affected by the support texture, which has led to variations in nickel ferrite stabilization on the support surface and is well reflected in the ultimate catalytic performance.